台阶式溢流坝消力池水跃特性

Hydraulic jump characteristics in stilling basin of stepped spillways

通过模型试验研究了台阶式溢流坝3种坝坡及台阶高度时的压强、水跃长度及特性,提出了计算水跃长度的经验公式.研究表明：远驱水跃时部分水股向上跃起,形成不完全的挑射水流,在水流跃离消力池底板的区域,压力趋于零或出现很小的负压,沿池底板时均压力和瞬时压力变化近似横向放置的“Z”字型;临界水跃时底板上的压力变化与远驱水跃类似,但均有所增大,负压消失;相对临界跃长Lj/yc增加,相对堰上临界水深yc/h增大,当yc/h＜1时相对临界跃长以线性增加,yc/h≥1时相对临界水跃增长的速度明显减慢,特别是当yc/h≥2.25以后,相对堰上临界水深对相对临界水跃长度影响很弱;随跃后水深和跃前底板压力增大水跃长度增加,光面溢流坝的水跃长度与台阶式溢流坝水跃长度的比值为1.1～2.4,这种差值在小流量时较大,随流量增加差值缩小;另外,坝面坡度对水跃长度影响较小.

Through model tests, this paper studies the pressure, the hydraulic jump length and the characteristic of hydraulic jump length, on the stepped spillways under three kinds of dam slope and step height, and suggests an empirical formula for calculation of hydraulic jump length. Results show that at downstream hydraulic jump, part of the water shares jump up and form incomplete jump flow. Pressure tending to zero or appearing negative occur at the flow spring still ing basin soleplate. Mean pressure change and instantaneous pressure change appear to be approximate horizontal placed ＂Z＂, at critical hydraulic jump. The pressure change on soleplate is similar to downstream hydraulic jump, but all increase and negative pressure disappear. Relatively critical hydraulic jump length Li/yc increases with relatively weir crest critical water depth yc/h. when yc/h 〈1, relatively critical hydraulic jump length increases linearly. When yc/h≥1, relatively critical hydraulic jump increases slowly, especially when yc/h≥2. 25, relatively weir crest critical water depth affects relatively critical hydraulic jump length weakly. Hydraulic jump length increases with rear depth of hydraulic jump and hydraulic jump forepart soleplate pressure. The ratio between slippery spillway hydraulic jump length and stepped spillway hydraulic jump length is 1.1 - 2.4. This difference is relatively large at small discharge and decreases with increasing discharge. Additionally, dam slope has less influence on hydraulic jump length.